Joint Astrophysics/Space Physics Seminar
"Ultra-Precise Spectrographs That Operate at The Diffraction Limit" by Professor Justin Crepp, Department of Physics, University of Notre Dame
Abstract: The Doppler radial velocity (RV) method continues to inform our understanding of extrasolar planets — their formation and evolution, orbital architectures, masses and composition, and demographics. Although much progress has been made in generating precise RV time series measurements, basic physics considerations related to the way that spectrographs are designed and built limit the utility of Doppler observations much below one meter per second. As a result, effects involving stability, image quality and spectral resolution, and consequently the handling of stellar activity, currently preclude the study of Earth-mass analogues orbiting Sun-like stars. In this talk, I will describe a new type of spectrograph that uses “extreme” adaptive optics to inject starlight directly into single mode fibers. By correcting for the image-blurring effects introduced by Earth’s turbulent atmosphere, I will argue that a diffraction-limited instrument can address outstanding questions in exoplanetary science by generating unprecedented RV precision. We are constructing the first-such spectrograph of this kind for the Large Binocular Telescope in Arizona. The instrument, named “iLocater,” will benefit from input images that achieve ~20 times higher spatial resolution than seeing-limited designs, enabling high spectral resolution (R=150,000-240,000) observations using an ultra-stable, compact optical design at low cost. This capability shows promise to open new vistas of exploration in the study of extrasolar planets and stellar astronomy.